Lecture09_Amplifiers_2up

Lecture09_Amplifiers_2up - EECS240 Spring 2008 Lecture 9...

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EECS240 – Spring 2008 Lecture 9: Amplifiers Elad Alon Dept. of EECS EECS240 Lecture 9 2 OpAmps and OTAs OpAmp OTA High voltage gain, high input impedance Voltage source output (low impedance) High “voltage” gain, high input impedance Current source output (high impedance) + - V i G M V i + -
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EECS240 Lecture 9 3 Resistive Feedback Open-loop gain: (Independent of R f ) Open-loop gain: G m R f Feedback loads the OTA How about large R f ? Lots of area, parasitic poles Need a different solution… EECS240 Lecture 9 4 How about Capacitive Feedback? At low frequency: No loading from feedback network (|Z f | = ) Gain drops at high frequency But this happens in all amplifiers Does this really work? Hint: what happens if you simulate this in SPICE?
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EECS240 Lecture 9 5 Capacitive Feedback cont’d Charge on v x is undefined – needs to be reset to
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This note was uploaded on 05/23/2008 for the course EECS 240 taught by Professor Eladalon during the Spring '08 term at University of Calgary.

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Lecture09_Amplifiers_2up - EECS240 Spring 2008 Lecture 9...

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